It is known to use in particular acid cation exchangers for the catalysis of chemical reactions, such as for example for the condensation of ketones or aldehydes with phenols to form bisphenols. Condensation reactions are known in the literature, such as for example the synthesis of bisphenols, which is generally carried out by acid-catalyzed reaction of phenols with carbonyl compounds. This last reaction is generally carried out under heterogeneous catalysis in fixed bed or fluidized bed reactors, as well as in reactive columns. Catalysts of cross-linked sulfonated polystyrene resins (acid ion-exchangers; cation exchangers) are normally used for example in the synthesis of bisphenols. These ion exchangers can optionally be chemically modified by covalently or ionically bound co-catalysts and are macroporous or in gel form, as is described in U.S. Pat. No. 4,191,843 and U.S. Pat. No. 3,037,052.
It is also known to subject in particular acid cation exchangers to a pre-treatment before they are used as catalysts in chemical reactions, in which for example elutable acid-containing constituents are removed from the catalyst bed, so that in the subsequent reaction they do not lead to the formation of undesired by-products. Such a pre-treatment, which is generally also connected with a dewatering of the washed ion exchanger and is normally termed conditioning, is indispensable in particular for the production of bisphenols using acid ion exchangers, and is described in WO-A 01/37992.
It is furthermore known that cation exchangers that are pretreated and are used for the synthesis of bisphenols can be unstable, as can be seen from the teaching of JP-A 000006296871 and JP-A 000006304479. JP-A 000006296871 now describes methods by which the handling, storage and transportation of the unstable catalyst can be avoided. The methods outlined here describe how the conditioning takes place in the reactor subsequently used for the catalysis. JP-A 000006296871 thus describes a method in which the conditioning takes place beforehand in the reactor used for the catalysis, so that a storage and a transportation of the unstable ion exchanger is not necessary, but the reactor for the actual catalysis cannot simultaneously be used at the time of the conditioning. A treatment of the ion exchanger that is carried out under stationary conditions, for example in a reaction apparatus, is likewise described in EP-A 1239958. The implementation of a pre-treatment/conditioning of ion exchangers in the reaction apparatus has the disadvantage that the reaction apparatus during the conditioning is not available for the production process and the catalyst conditioning thus means a production breakdown.
In order to avoid such a production breakdown, it is possible to carry out the necessary conditioning of the ion exchanger in a separate conditioning apparatus decoupled from the actual production process. This however means additional investment costs, which have an adverse influence on the economy of the overall production process. This effect is all the more pronounced the more the conditioning apparatus is only partially utilized, as is often the case in catalyst replacements that are carried out batch-wise.
The preconditioning of a cation-exchange resin suspension for the catalyzed reaction of acetone with phenol to form bisphenol A is described in WO-A 01/37992. WO-A 01/37992 also describes how this preconditioning can be carried out in an external vessel upstream of the reactor, but does not describe how such a preconditioned ion-exchange resin suspension can be stored for a prolonged period or transported to other production sites and transferred there to the respective reactor, without the preconditioned ion-exchange resin suspension losing its properties that are important for the catalysis.
Such a procedure means a restriction as regards the efficient provision, arrangement and utilization of apparatuses and parts of equipment for the catalyst pre-treatment and conditioning, in particular for users operating a plurality of production plants in which a repeated catalyst exchange is necessary.
The object of the invention is accordingly to provide a process that enables the preconditioned ion-exchange resin suspension to be stored and also transported over prolonged periods and then decanted into a reactor, without the ion-exchanger losing over this time the necessary properties as a reaction catalyst. By means of such a process the preconditioned ion-exchange resin suspension is independent of the production site, for example of the bisphenol synthesis, contrary to the teaching of JP-A 000006296871 and JP-A 000006304479.
Contrary to the preconception disclosed in the teaching of JP 000006296871 and JP 000006304479, it is now found that pretreated, conditioned cation exchange resin suspensions for the bisphenol synthesis can perfectly well be stored, transported and then decanted into a reactor, without thereby losing their activity and their usability for this synthesis, if in this connection the process described hereinafter is employed for the storage of preconditioned ion-exchange resin suspensions.